1. Field of the Invention
Apparatuses consistent with the present invention relate to a zoom lens that has various focal lengths and is applicable to photo cameras, television cameras and various optical system.
2. Description of the Related Art
In recent years, due to the increasing usage of digital cameras or video cameras using solid-state imaging devices, such as charge-coupled device (CCD) imaging devices or complementary metal-oxide semiconductor (CMOS) imaging devices, these imaging optical devices have become more and more compact, lightweight, and inexpensive. Simultaneously, users' demand for high performance, for example, a high variable magnification ratio and a good image quality, has gradually increased.
As a result, various designs for auto-zoom lenses whose focal lengths vary within wide ranges have been proposed. In order to embody various focal lengths, an auto-zoom lens includes a plurality of groups of lenses so that some groups of lenses are fixed and the remaining groups of lenses move. However, it is difficult to achieve a required image quality over the entire variation range of focal lengths. For example, a good image quality may be actually ensured at only three zoom positions. Therefore, it is needed to design a zoom lens capable of solving this problem.